The present invention concerns a link, provided for connecting a bracelet to a watch case, the latter including an exterior or decorative element which defines at least partially its limits in the longitudinal direction of the bracelet, the exterior element being obtained by a method including a sintering step.
The invention concerns more generally the field of watch bracelets partially made of hard materials, such as ceramics, intended to be assembled on watches whose case includes exterior parts made of a hard material.
A bracelet of this type, including a more or less flexible inner structure assuring the function of a core or frame and at least partially covered by decorative elements is known to those skilled in the art.
American U.S. Pat. No. 5,365,753 discloses a bracelet, in particular for a watch, including an inner chain formed of articulated links, connected to each other by hinges. Each of these links, formed of two structural elements, is covered by an exterior decorative element made of ceramic material. Further, each link includes means for holding the corresponding decorative element so as to obtain an advantageous aesthetic effect, insofar as the various hinges connecting the links to each other are never visible.
However, this structure has certain limits in its application, as do generally known bracelets of this type in the prior art. Indeed, the decorative parts made of hard material, for example, ceramic material, are obtained by methods including a moulding step followed by a sintering step. During this sintering step, these parts undergo a contraction, i.e. a significant reduction in volume, via the combined actions of heat and pressure, this contraction being able to be more than 30% of the initial volume. Commonly implemented methods currently allow such parts to be manufactured with tolerances on the dimensions of the order of 0.5 to 1%, the sintering step making it difficult to obtain lower tolerances. It should be noted that these tolerances fluctuate as a function of the batches of raw material used.
The tolerances involved result, for example, in uncertainties of the order of a fifth of a millimetre over the length of a ceramic watchcase of 3 centimetres. Insofar as this type of watchcase is in the top of the watchmaking range, such uncertainty is difficult to accept for manufacturers.
Consequently, the prior art provided manual machining, after the sintering step, in order to eliminate the various play existing between the ceramic elements of the exterior parts of such a watch.
However, faced with the increasing client demand for such products, the number of watchmaking parts including ceramic decorative elements to be manufactured has greatly increased over the last few years, making the machining steps very laborious, given the quantity of parts to be processed. Moreover, this machining step is made more difficult because of the increasing complexity of the geometry of watch cases currently being made, which makes it complicated to lock the part into a given position in order to work on it.
It should be noted that this problem is all the more inconvenient because the decorative parts to be manufactured are large. In particular, the aforementioned manufacturing tolerances have detrimental impact on the watchcase, whose dimensions are generally larger than those of the bracelet links. Likewise, the more the manufacturer of such timepieces wishes to make bracelet links of greater dimensions, the more difficulty he will have in making junctions between the watch case and the bracelet or between bracelet links having a satisfactory aesthetic appearance.
The main object of the present invention is to overcome the aforementioned drawbacks of the prior art and to improve the aesthetic appearance of existing timepieces.
The invention therefore concerns a link for a watch bracelet of the aforementioned type, characterised in that it includes a first hollow element provided with first means for attaching it to the bracelet, a second element one part of which is nested in the first element and carrying second means for attaching said second element to the watch case and a third exterior decorative element, secured to the first element and at least partially covering the second element on the side of the second attaching means. The link according to the present invention is further characterised in that it includes a mechanical device allowing a translation of the first element with respect to the second element in the direction of the bracelet, so as to apply the third decorative element against the decorative element of the watchcase.
As a result of these features, it is possible to adjust the position of the bracelet with respect to the watchcase in order to correct the problems of manufacturing tolerances. As a result of such an adjustment an uninterrupted junction is obtained between the bracelet and the watchcase, which is advantageous from the aesthetical point of view.
In a first embodiment, the first element is hollow and the mechanical device is housed therein in the form of resilient means, such as one of more springs or an elastomer block. These resilient means exert a return force on the first element so as to bring it closer to the second end of the second element, the latter carrying the second attaching means and extending outside the first element through an aperture made in one wall of the latter. The result obtained by applying this return force is to bring the third decorative element of the link permanently closer to the watch case, independently of the value of the watch case""s manufacturing tolerances.
In an alternative embodiment, the volume left free by the mechanical device in the first hollow element is made impervious or sealed with respect to the external environment, as a result of the use of a particular structure and suitable sealing gaskets. This feature may be advantageously used to house various electronic components or even a battery in the first element.
In another embodiment, the mechanical device includes means for adjusting the position of the bracelet with respect to the watchcase. In other words, the adjustments are carried out when the bracelet is attached to the case, such that the junction is uninterrupted, and can be modified subsequently. These means may, in particular, include an adjusting screw, connected in various ways to the various elements of the link according to the present invention.
The screw may in fact be housed in a hole arranged in the second link element, buffers may be arranged on the screw on either side of the second element, these buffers being capable of being moved in a perpendicular direction to that of the bracelet, at least one of the buffers being provided with a screw thread. Moreover, at least one oblique guide with respect to the direction of the bracelet is arranged, for each buffer, on the wall of the first element including the aperture and/or on the first end of the second element, so that each of the oblique guides is stopped against the corresponding buffer, and that any rotation of the screw is able to modify the distance between the buffers and thus the relative positions of the first and second elements.
This variant advantageously allows very precise adjustment of the position of the first element with respect to the second element, and thus the position of the third decorative element with respect to the watchcase.
In another variant, the first and second link elements may also respectively have lateral surfaces located opposite each other which are at least partially in contact with each other, the screw passing through an aperture in the second element which has an elongated oblong section, the threaded end of the screw being housed in a tapped hole arranged through said surface of the first element whereas the head of the screw is, in the screwed in position, stopped against a face of the second element opposite said surface in contact with the first element.
This variant allows a lower level of adjustment precision to be obtained than that accessible with the preceding variant, but has the advantage of greater construction simplicity.
Another variant provides that the head of said screw is housed so as to rotate freely in the wall of said first element opposite said wall including the aperture, whereas the threaded end is housed in a tapped hole of said end of the second link element located inside said first element.
Thus, even if the head of the screw is not as accessible as in the preceding variants, a high level of precision can be obtained while having great construction simplicity.
The invention also concerns a watch bracelet as defined in claim 18 annexed hereto.
The wristwatch thus obtained therefore has an advantageous aesthetic appearance because of the continuity existing between the bracelet and the case.
Each of the links of the bracelet may also include a similar structure to that of the link forming the junction between the bracelet and the watchcase, so as to assure continuity of the junctions across the entire watch.